How to associate one table non Primary key to others tables non foreign key in CakePHP2?

Need Help
1

Example:

  1. Staff(relation_id(non primary key))
  2. Teacher(teacher_id(non primary key))
  3. Vendors(vendor_id(non primary key))

Now, teacher_id = relation_id for the relationship with the Teacher to Staff
vendor_id = relation_id for the relationship with the Vendors to Staff

In, Staff table I’m associating in Staff.php like below:

public $belongsTo = array(
        'Teacher' => array(
            'className' => 'Teacher',
            'foreignKey' => false,
            'conditions' => array('Teacher.is_deleted' => 0, '`Staff`.`relation_id` = `Teacher`.`teacher_id`'),
            'fields' => '',
            'order' => '',
            'dependent'    => false
        ),
        'Vendor' => array(
            'className' => 'Vendor',
            'foreignKey' => false,
            'conditions' => array('Vendor.is_deleted' => 0, '`Staff`.`relation_id` = `Vendor`.`vendor_id`'),
            'fields' => '',
            'order' => '',
            'dependent'    => false
        ),
    );

But its not working, can anyone have idea in cakephp2?